members, bare.

This represents all that Scrooge is at this moment, for he is an old man, but within him is still this child. It is Scrooge's childhood that causes him to loathe Christmas. And The Ghost of Christmas Past reveals this when it shows Scrooge as a very "lonely boy . . . reading near a feeble fire" at a boarding school during Christmas, while all the other boys have gone home for the holiday. Then it shows Scrooge at another Christmas "walking up and down despairingly" at another boarding school. These Christmases scarred him psychologically.

However, this image also suggests that Scrooge should not let his past affect his present and future. This is revealed in the duality of the child and old man image. Man is born innocent and loses this innocence through experience, but as he ages, he returns to a higher state of innocence. This notion can be seen in the combination of the child and the old man in the spirit. However, Scrooge never regained his innocence as he aged; he became more calloused and bitter toward mankind and Christmas. He never progressed from the experiences that he had during those two Christmases alone.

The idea of the past being a major factor in Scrooge's life is further revealed in the strangest description of the Ghost when it changes from

being now a thing with one arm, now with one leg, now with twenty legs, now a pair of legs without a head, now a head without a body: of which dissolving parts, no outline would be visible in the dense gloom wherein they melted away. And in the very wonder of this, it would be; distinct and clear as ever.

The body parts represent the dysfunctional mentality of Scrooge; he is so disjointed from reality, from mankind, and from all that is good.

The description of the light coming from the top of the Past's head clearly symbolizes the truth, and the truth of the matter is Scrooge had a terrible childhood and is taking it out on the world, but the Past shows Scrooge that his past wasn't entirely bad, for his sister Fan was a positive, as was Fezziwig. Ultimately, Scrooge had to be shown his past in order to fully understand himself.

The first of the three spirits looks like a cross between a child and an old man.  Dickens says that it looks like an old man with white hair, but it has no wrinkles and is about the size of a child.  In addition to that, it looks like it's really strong.  Finally, it is carrying holly (a winter plant) but also spring flowers.

To me, its appearance reinforces what it is supposed to be teaching Scrooge.  I think it is supposed to be teaching him that he used to be a better person and that part of him is still alive somewhere in him.  So it is telling him that he is a mix of the old man he is now and the kid he was -- just like the spirit is a mix of old and new, winter and spring.

The first spirit to appear in the novel is Marley's ghost; indeed Stave One of the novel is entitled "Marley's Ghost." Scrooge first sees Marley's face in the door knocker, and then Marley appears as a figure in Scrooge's bedroom. Marley explains to Scrooge that, as a spirit, he is condemned to "wander through the world . . . and witness what it cannot share, but might have shared on earth, and turned to happiness." Dickens has already mentioned that Scrooge and Marley were "of one mind" in life, so when Marley explains that he now carries the chain he "forged in life" through his behaviour, he is warning Scrooge that the same will happen to him if he persists. Marley is explicit in his reasons for speaking to Scrooge, although he notes that he has sat beside him many times before and does not understand why, on this particular occasion, he should be visible. Marley is here "to warn you, that you have yet a chance and hope of escaping my fate." 

Marley, effectively, is a herald for the other spirits--he notes that these spirits will visit Scrooge as a result of Marley's "procurement" of them. He also explains that the spirits' visits are the only way that Scrooge can "hope to shun the path [Marley] treads" in his "fettered" death. 

The first of the three spirits Marley describes, the Ghost of Christmas Past, duly appears to Scrooge as Marley said, to remind Scrooge of his own past as the first step on his journey to redemption.  

By allowing him to become nostalgic, the Ghost of Christmas Past was touching into Scrooge's emotions, things he had long discarded.  Scrooge as an adult saw the world as a cold and unhappy place.  By allowing him to see times when his world was happy, and when he himself was happy, the spirit is preparing him to see Christmas Present with an optimistic and not cynical attitude.  If the Ghost of Christmas Present had appeared to Scrooge with no preparation, he would have likely ignored everything he saw.

The first Christmas Spirit is a "strange figure. This spirit has the proportions of a child, but resembles an old man, although there are no wrinkles on its face. Dressed in a tunic of white that is cinched with a glorious belt of a beautiful sheen. The oddest thing about this small spirit is the bright light that jets out from the crown of its head.

Scrooge is amazed when he sees this spirit whose hair is white, but has a face that is without wrinkle and has the bloom of youth on its skin. The spirit's arms are exceptionally long and muscular, and the hands, too, seem uncommonly strong; in one hand is a branch of holly in contrast to the bottom of the tunic that is trimmed with summer flowers. Like the arms, the legs and feet are bare. Under the one arm is an extinguisher for a cap, to cover the light emanating from its head.
Then, when Scrooge examines the belt, he notices that one area lights up, then another and the first area is dark so that the spirit seems to be dissolving in one place and reappearing in another. Then, the spirit would appear whole again. 
When Scrooge asks this strange spirit if it is the one he has been told to expect, and the spirit affirms that it is: "I am the Ghost of Christmas Past." 

The first spirit is the Ghost of Christmas Past. He takes Scrooge back to some scenes from his earlier years. This part of the book provides us with a useful bit of exposition concerning Scrooge's story, helping us to get a better understanding of him and how he became such an unpleasant old miser.

We learn that Scrooge was desperately unhappy as a boy and was sent away to a boarding school he thoroughly detested. We also learn that Scrooge was very close to Fan, his kind, loving sister who pleaded with her father to allow young Ebenezer to return home and escape his miserable schooldays.

The Ghost of Christmas Past shows us another side of Scrooge, one more human and vulnerable. He even used to like Christmas in the past years, enjoying the seasonal hospitality of his kindly employer, Mr. Fezziwig. However, Scrooge became greedy and ambitious, putting money ahead of all his relationships. He was engaged to be married to Belle, but she broke off the engagement when she realized what kind of a man her fiancé was becoming. The Ghost of Christmas Past presents Scrooge with a scene of Belle, now happily married, enjoying Christmas Eve with her family on the night that Jacob Marley passed away.

In A Christmas Carol, the Ghost of Christmas Past is the first to visit Scrooge. While Dickens does not specifically state that this ghost is the most important, he alludes to this fact in two important ways.

First of all, the physical description of the Ghost of Christmas Past emphasises its importance in the story. It springs a "bright clear jet of light" from its head, is dressed in the "purest white" and its belt "sparkled and glittered." This angelic description contrasts sharply with the other ghosts who visit Scrooge that night: the Ghost of Christmas Present is far more ordinary and human while the Ghost of Christmas Yet to Come is simply a hooded figure. No other ghost receives as much attention from Dickens nor such a wondrous and detailed description. 

Secondly, it can be argued that the Ghost of Christmas Past shows Scrooge the most important powerful images in the book. These images, of his childhood and his former relationship with Belle, not only explain how Scrooge became so miserly and greedy, they also prompt the important process of transformation. Without seeing these shadows of the past, Scrooge would never accept that he needed to change and he could not have achieved this without the Ghost of Christmas Past.